The present invention relates to an electrochromic mirror, and more particular to an electrochromic mirror having an alternative color and desired electrochromic property by incorporating therein a specific reflective layer. The present invention further relates to a reflective layer imparting an alternative color and desired electrochromic property to an electrochromic mirror.
Glare is one of the troublesome factors when driving a vehicle. Many efforts have been made to solve the glaring problem. One of the most effective ways is to provide an electrochromic unit for the rearview mirror of the vehicle. The electrochromic unit deepens the color and thus reduces the reflectance of the mirror according to the degree of the glare, thereby minimizing the glaring effect. FIG. 1 is a schematic diagram showing a conventional electrochromic unit for use in a rearview mirror assembly of a vehicle to achieve the reflectance-adjustment purpose by changing the color of the rearview mirror.
The electrochromic unit includes two glass substrates 11 and 12 positioned parallel to each other, and spaced apart by a distance of a micrometer-to-millimeter order. On each of the inner faces of the glass substrates, a transparent indium-tin-oxide (ITO) coating 13, 14 is provided as an electrode for electric conduction. The space 15 between the two glass substrates 11 and 12 is filled with an electrochromic solution and sealed with a material 16 inert to the electrochromic solution, e.g. epoxy. Furthermore, a reflective layer 17 is coated on the other side of the glass substrate 14 opposite to the glass substrate 12 for providing proper mirror reflectance. By applying a voltage across the ITO cathode and anode 13 and 14, the color of the electrochromic solution will change accordingly. With the increase of the glare light intensity, the voltage applied to the electrochromic unit increases, and the color of the mirror becomes darker.
In general, the electrochromic solution includes an anodic compound which undergoes a reversible color change when its valence state is altered due to oxidation, a cathodic compound which undergoes a reversible color change when its valence state is altered due to reduction, and a solvent which solubilizes the anodic and cathodic compounds but keeps chemically inert to the other constituents of the electrochromic solution. The electrochromic solution may optionally further includes an electrolyte material for enhancing the conductivity of the electrochromic solution. Please refer to U.S. Pat. Nos. 4,902,108, 5,679,283, 5,611,966, 5,239,405, 5,500,760 and 6,211,994B1 which are incorporated herein for reference, to realize examples of the anodic compound, cathodic compound, solvent and electrolyte material contained in conventional electrochromic solutions.
In the prior art, the reflective layer 17 is generally made of aluminum. Due to poor adhesion between glass and aluminum, the reflective layer 17 is readily stripped off the glass substrate 12 so as to reduce lifetime of the rearview mirror assembly.
FIG. 2 is a schematic diagram showing another conventional electrochromic unit for use in a rearview mirror assembly of a vehicle to achieve the color-change purpose. The electrochromic unit of FIG. 2 includes two glass substrates 21 and 22 positioned parallel to each other, and spaced apart by a distance of a micrometer-to-millimeter order. On each of the inner faces of the glass substrates, an electrically conductive electrode 23, 24 is provided. The space 25 between the two glass substrates 21 and 22 is filled with an electrochromic solution and sealed with a material 26 inert to the electrochromic solution, e.g. epoxy. Depending on the required level of electric conduction, the electrode 23 is made of a transparent material such as indium-tin-oxide (ITO) or a transparent composite material such as ITO/metaL/ITO. The electrode 24 could also act as a reflective layer by utilizing a metallic material having both the high reflectivity and the high electrical conductivity. Thus, the process for fabricating the electrochromic unit can be exempted from making the reflective layer 17 in FIG. 1. The metallic material used in the electrode 24 is usually silver (Ag) or silver alloy such as silver-gold (Ag/Au) alloy, silver-platinum (Ag/Pt) alloy, silver-palladium (Ag/Pd) alloy and the like. However, since the electrode 24 is arranged between the glass substrate 22 and electrochromic solution 25 and in contact with the seal 26, the fabrication of the electrode 24 in view of the corrosion and the electrical property change problems are critical. For example, a base layer 27 between the electrode 24 and the glass substrate 22 is required for the purpose of attaching the electrode 24 onto the glass substrate 22. Furthermore, in order to prevent the electrode 24 from being corroded by the electrochromic solution 25, a protective layer 28 is further provided between the electrode 24 and the electrochromic solution 25 with a proviso that the electrical property of the electrode 24 is not impaired. Although the electrode 24 provides both the high reflectivity and the high electrical conductivity, the process for fabricating such electrochromic unit of FIG. 2 involves complicated steps and high producing cost.
It is an object of the present invention to provide a reflective layer which provides suitable reflectance for the mirror and excellent adhesion to the glass substrate of an electrochromic mirror assembly.
It is another object of the present invention to provide an electrochromic mirror which is easily produced and has an alternative color in response to the glare, compared to the conventional ones.
In accordance with an aspect of the present invention, there is provided an electrochromic mirror for performing color change in response to a voltage applied thereto. The electrochromic mirror comprises a first substrate, a second substrate, a first and a second electrodes, an electrochromic composition and a reflective layer. The first substrate being light transmissible. The second substrate is positioned substantially parallel to the first substrate, and spaced apart from the first substrate by a predetermined clearance to form a space therebetween. The first and the second electrodes are provided on opposite surfaces of the first and second substrates facing the space, respectively, for providing a voltage, the first electrode being light transmissible. The electrochromic composition is disposed in the space between the first and second substrates for performing color change in response to the voltage. The reflective layer is made of aluminum-titanium (Al/Ti) alloy and disposed on the second substrate for partially reflecting the light entering from the first substrate back to the first substrate.
In an embodiment, the first and second substrates are made of glass.
In an embodiment, the first and the second electrodes are made of indium tin oxide (ITO).
In an embodiment, the reflective layer is disposed on the second substrate opposite to the second electrode. Furthermore, the electrochromic mirror comprises an intermediate layer between the second substrate and the reflective layer for cooperating with the reflective layer to provide different color from that resulting from only the reflective layer.
In an embodiment, the intermediate layer is made of indium tin oxide (ITO).
In an embodiment, the reflective layer is disposed between the second substrate and the second electrode.
In accordance with another aspect of the present invention, there is provide an electrochromic mirror for performing color change in response to a voltage applied thereto. The electrochromic mirror comprises a first substrate, a second substrate, a first and a second electrodes, an electrochromic composition and a composite reflective layer. The first substrate is light transmissible. The second substrate is positioned substantially parallel to the first substrate, and spaced apart from the first substrate by a predetermined clearance to form a space therebetween. The first and the second electrodes are provided on opposite surfaces of the first and second substrates facing the space, respectively, for providing a voltage, wherein the first electrode is light transmissible. The electrochromic composition is disposed in the space between the first and second substrates for performing color change in response to the voltage. The composite reflective layer is disposed on the second substrate for partially reflecting the light entering from the first substrate back to the first substrate. Preferably, the composite reflective layer is made of an indium tin oxide (ITO) layer and a highly reflective layer.
In an embodiment, the first and second substrates are made of glass.
In an embodiment, the first and the second electrodes are made of indium tin oxide (ITO).
In an embodiment, the highly reflective layer is made of a material selected from a group consisting of chromium (Cr), aluminum-titanium (Al/Ti) alloy and silver (Ag).
In an embodiment, the composite reflective layer is disposed on the second substrate opposite to the second electrode.
In an embodiment, the indium tin oxide (ITO) layer of the composite reflective layer is disposed between the second substrate and the highly reflective layer.
In accordance with another aspect of the present invention, there is provided an electrochromic mirror for performing color change in response to a voltage applied thereto. The electrochromic mirror comprises a first substrate, a second substrate, a light-transmissible electrode, a composite electrode and an electrochromic composition. The first substrate is light transmissible. The second substrate is positioned substantially parallel to the first substrate, and spaced apart from the first substrate by a predetermined clearance to form a space therebetween. The light-transmissible electrode is disposed on the first substrate facing the space. The composite electrode is made of an indium tin oxide (ITO) layer and a highly reflective layer and disposed on the second substrate facing the space for cooperating with the light-transmissible electrode to provide a voltage. The electrochromic composition is disposed in the space between the light-transmissible electrode and the composite electrode for performing color change in response to the voltage.
In an embodiment, the highly reflective layer is made of a material selected from a group consisting of chromium (Cr), aluminum-titanium (Al/Ti) alloy and silver (Ag).
In an embodiment, the highly reflective layer is disposed between the second substrate and the indium tin oxide (ITO) layer of the composite reflective layer.
In accordance with another aspect of the present invention, there is provided a reflective layer of an electrochromic mirror for partially reflecting incident light from an image. The reflective layer comprises an aluminum-titanium (Al/Ti) alloy layer. In an embodiment, the reflective layer further comprises an indium tin oxide (ITO) attached to the aluminum-titanium (Al/Ti) alloy layer.
In accordance with another aspect of the present invention, there is provided a reflective layer of an electrochromic mirror for partially reflecting incident light from an image. The reflective layer comprises is immediately adjacent indium tin oxide (ITO) layer and highly reflective layer. In an embodiment, the highly reflective layer is made of a material selected from a group consisting of chromium (Cr), aluminum-titanium (Al/Ti) alloy and silver (Ag).
The above objects and advantages of the present invention will become more readily apparent to those ordinarily skilled in the art after reviewing the following detailed description and accompanying drawings, in which: